Update: For more information on the Weather Alerts System, this FEMA page provides a full description of the one way alert system. Note that the ability to get notifications of AMBER alerts and Emergency Alerts can turned off via a new set of buttons found at the bottom of the Settings > Notifications page on the iPhone 5 under "Government Alerts".
Back in June, TUAW reported on the new Wireless Emergency Alerts system from the US National Weather Service. At that time, the system -- which alerts smartphone owners in areas under a severe weather warning -- didn't support iPhones and the system was available on Sprint, Verizon and T-Mobile networks plus a handful of AT&T cities.
Well, the system is apparently working with the iPhone 5 at present, as I received the alert you see at right earlier today. The area where I live is currently under a blizzard warning, so I received the message. My wife uses an iPhone 4S on AT&T and did not receive the alert, and Erica Sadun -- with the same equipment and network -- was also left in the dark. I'm not sure if that's because they're on an "older" iPhone model or if AT&T hasn't initiated the service in the Denver area.
Anyway, it's great to see this service working. It doesn't require users to sign up, and it's a powerful way to get your attention about upcoming weather emergencies including ice and dust storms, blizzards, extreme winds, flash floods, tornadoes, hurricanes, typhoons and tsunamis.